On CNN's "State of the Union," Robby Mook, who heads up Clinton's presidential campaign, told Jake Tapper that "experts" have told the campaign that "Russian state actors broke into the DNC, stole these emails, and other experts are now saying that the Russians are releasing these emails for the purpose of actually helping Donald Trump."

He added that he didn't think it was "coincidental that these emails were released on the eve of our convention." Mook didn't provide evidence that Russians are behind the hack or release of emails, but when pressed by Tapper, he emphasized the accusations came from unnamed "experts."

The Clinton campaign is now suggesting that the Russians also accessed internal emails regarding the contentious Democratic primary. On Friday, WikiLeaks released emails that showed Democratic National Committee Chairwoman Debbie Wasserman Schultz and other DNC staffers disparaging the Bernie Sanders campaign. (Schultz has reportedly been replaced as chair of the Democratic National Convention over the email scandal.) In one email, staffers dismissed Sanders' campaign as "a mess" and added that his campaign "never had their act together." The 20,000 pages of hacked emails nearly overshadowed Clinton's announcement Saturday that Virginia Senator Tim Kaine would run as her vice president.

Clinton's campaign has previously criticized Trump for his praise of Russian leader Vladimir Putin, a point that was highlighted this past week when Trump suggested that without sufficient financial contributions, the US under his leadership may not honor NATO commitments to defend European allies against attacks from Russian.

Trump campaign chairman Paul Manafort dismissed Mook's comments on Sunday, telling ABC's "This Week" that the allegations were "absurd," and that "there was no basis for it." He added that this was just a smokescreen by the Clinton campaign, which doesn't want to talk about what's in the emails.

Updated at 12:24 p.m. PT to add that Schultz has reportedly been replaced as chair of the Democratic National Convention.